Vehicles with often incorporate a transmission fluid or engine oil cooler mounted in the liquid coolant outlet tank of the engine cooling radiator as a convenient means to cool those fluids. Typically, the radiator consists of a basic core with header tanks on each side, and flattened metal coolant flow tubes, generally aluminum, extending between the tanks. Each tank is a plastic box open on one side, the open side being clinched to a metal header plate that receives the ends of the radiator flow tubes and keeps them regularly spaced apart. As shown in co assigned U.S. Pat. No. 5,645,125, a conventional oil cooler consists of a series of plates stacked into a general box shape, which is installed inside the radiator outlet tank, with sealed inlet and outlet pipes running through the radiator tank wall. This requires very careful sealing not only of the many joints between the oil cooler plates, but also of the metal to plastic interface between the cooler pipes and radiator tank wall. That interface requires mechanical sealing, such as threaded fittings and compressible O rings, which is not as robust as a brazed joint of the type found between the ends of the radiator flow tubes and the radiator tank header plate. Such an oil cooler is also quite massive and heavy, and blocks a good deal of flow area within the radiator tank.
A relatively newer proposed oil cooler construction is incorporated within all metal (aluminum) header tanks of an all metal core. In effect, the tank and the header plate are one and the same part, or at least formed of the same material. An example may be seen in co assigned U.S. Pat. No. 5,823,250. There, the header tank itself has an extruded body, with integral slotted header plate and integral internal oil cooler passage. End caps are brazed on the seal the ends of the header tanks and the internal oil cooler passage simultaneously. This type of integral oil cooler construction depends on the header tank being made as an extrusion, which is not always practical, because of weight and cost considerations, and most radiator tank constructions still consist of a plastic tank clinched with a gasket seal to a metal core header plate.
An alternate type of oil cooler is a simple air-oil cooler, in which a small, separate core, similar in design to a small radiator of all metal construction, has pressurized oil pumped through its interior and ambient air forced over its finned exterior. Such a separate heat exchanger for the oil (ortransmission fluid) is an obvious extra expense, and requires its own space to be mounted to the vehicle, typically in the engine compartment. Such "real estate" on the vehicle is becoming increasingly rare and expensive. It would be a cost and space advantage to somehow to utilize only the space occupied by the existing radiator and, if possible, at least some of the existing components of the radiator. While the known in tank type of oil cooler does so, to an extent, it still constitutes a heavy and expensive solution.
In tank oil coolers of differing construction are known, at least in the published patent art. Co assigned U.S. Pat. No. 5,366,005 discloses a radiator with spaced header tanks, within one of which a helical round oil cooler tube is arrayed. One end of the helical, round cross sectioned tube exits the radiator header tank wall to act as an oil inlet, to which it is sealed in an unspecified manner. The other end of the helical tube serves as an outlet into a sealed, separate oil chamber formed at the bottom of either a radiator header tank or, in an alternate embodiment, at the bottom of a condenser header tank. From the oil chamber, oil enters a plurality of flow tubes, similar to the coolant or refrigerant flow tubes in the main body of the radiator or condenser, and running parallel thereto. These separate tubes allow the air that is forced through the condenser and/or radiator to further cool the oil subsequent to the initial cooling received in the liquid cooling it first receives in the radiator header tank The dedicated oil cooler tubes empty into yet another sealed and separate oil outlet chamber in the opposite header tank. Such separate oil inlet and outlet chambers at the bottom of the radiator header tanks would represent a serious departure from the typical radiator header tank construction, especially in the case of the more typical plastic radiator tank, and would be very difficult to seal. Such sealing would be critical, however, as the oil would absolutely have to be rigorously sealed from the radiator coolant.
While it would be very difficult to create a suitable seal for such dedicated oil inlet and outlet chambers in the header tank, the manufacture of the conventional, slotted header plate, and the subsequent leak tight brazing of the radiator coolant flow tubes to the header plate slots, is a well understood and well controlled process. The flattened metal flow tubes, typically extruded or fabricated aluminum, are inserted through closely matching slots formed through the header plates. The surrounding interface between the two has a well controlled gap width. Braze material provided on the surface of either the flat metal tube or the header plate is melted when the core itself is brazed, and drawn into the tube end-slot interface to form a simple, consistent and leak proof joint. If similar materials and techniques alone could be used to form both the liquid and air cooled parts of an integrated oil cooler, such a design might find practical application.